We report electro-optical measurements of BaTiO3/ZnO heterostructures grown by pulsed laser deposition. The optical properties of the heterostructures were examined with and without an applied bias. A change in the heterostructure optical properties is found and attributed to a linear electro-optical effect causing a change in the band gap. Moreover the formation of an electric polarization in the BaTiO3 layer causes a remanent change in the dielectric function if the bias is removed. The change could be estimated to be around 5 meV. (C) 2010 Elsevier B.V. All rights reserved.